Der OBS501 verfügt über duale Rückstreu- und Seitenstreusensoren, einen Verschließmechanismus, der die Linse sauber hält und eine nachfüllbare Biozidkammer zur Vermeidung von Bewuchs wie der OBS500. Bei höheren Sedimentgehalten arbeitet er aber besser U.S. Pat. No. 8429952 (OBS® is a registered trademark of Campbell Scientific.).
Der OBS501 wurde so konstruiert, dass Sand oder andere Partikel nicht zwischen Linse und Abdeckung geraten können, wodurch sich die Abdeckung nicht mehr gut bewegen ließe. Durch Spülen der Optik werden zusätzlich Partikel entfernt.
Wenn der OBS501 merkt, dass der Motor der Abdeckung stärker als normal arbeiten muss, wird die Abdeckung leicht vor- und zurückbewegt, um Sandkörner zu entfernen, bevor die Abdeckung ganz geöffnet oder geschlossen wird.
Design features of the OBS501 include the combination of a backscatter sensor (better at measuring higher turbidity) with a second sidescatter sensor (better at measuring lower turbidity). It has a shutter that is opened only during measurements, which reduces the time that algae or other organisms can cling to its optics.
The OBS501 is constructed to prevent sand grains or packed sediment from getting wedged between the shutter and sensor body, which inhibits the shutter’s movement. To do this, the OBS501's shutter and body were designed to eliminate parallel surfaces between moving parts wherever possible. The probe also uses a flushing action that moves the sediment down and out of the cavity behind the shutter.
To prevent biofouling and ensure better measurements, the OBS501 incorporates the ClearSensor Method (U.S. Patent No. 8,429,952. This method uses a shutter/wiper mechanism to protect and clean the optics. With the ClearSensor method, a chamber is also filled with a biocide that continuously leaches out over the optics while the probe shutter is in the closed position. ClearSensor® and OBS® are registered trademarks of Campbell Scientific.
The OBS501 can sense if the shutter’s motor is working harder than normal. If it is, the shutter moves slightly back and forth to dislodge sand grains before fully opening or closing.
Campbell Scientific offers a disposable, plastic sleeve that can make cleanup a snap, as well as a copper sleeve that can provide additional protection, especially in sea water.
Dual Probe | 90° sidescatter and backscatter |
Measurement Range | 0 to 4000 NTU |
Active and Passive Antifouling | Shutter, wiper, biocide, copper, optional removable sleeve |
Accuracy | ±2% of reading or 0.5 NTU (whichever is greater) |
Operating Temperature Range | 0° to 40°C |
Storage Temperature Range | 0° to 40°C |
Temperature Accuracy | ±0.3°C |
Emitter Wavelength | 850 nm |
Power Requirements | 9.6 to 18 Vdc |
Measurement Time | < 10 s |
Maximum Submersion Depth | 100 m (330 ft) |
Diameter | 4.8 cm (1.88 in.) |
Maximum Cable Length |
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Length | 27 cm (10.63 in.) |
Weight | 0.59 kg (1.30 lb) |
Power Consumption |
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Quiescent | < 200 µA |
Measurement | < 40 mA |
Communication | < 40 mA |
Active Shutter Motor | < 380 mA |
Outputs |
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SDI-12 | Version 1.3, 1200 bps |
RS-232 | 9600 bps, 8 data bits, 1 stop bit, no parity, no flow control |
Analog | 0 to 5 Vdc |
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
Number of FAQs related to OBS501: 1
It used to be that NTUs were the unit for all turbidity sensors. In 2007, an ASTM committee formed and established different units for each category of turbidity sensor technology, and there are many. Backscatter sensors such as the OBS-3+ and the OBS501 have units of FBU (Formazin Backscatter Units), whereas ISO 7027 side-scatter sensors have units of FNU (Formazin Nephelometric Units). The side-scatter OBS501 and the ClariVUE™ sensors are part of this category. While sensors of different technical designs can be calibrated and measure Formazin the same, they will not make the same measurement in natural waters where size, shape, color, reflectivity, etc., of the particles vary. The ClariVUE™ sensor measurements will not match the OBS-3+ measurements in natural waters.